The $330-Million Monterey Peninsula Water Supply Project (MPWSP) took a step forward, as the California Supreme Court recently denied challenges to the sufficiency of the project’s Environmental Impact Report (EIR)/Environmental Impact Statement (EIS).

The long-awaited desalination plant located off the coast of Monterey is being developed by California American Water Company (CalAm) and is intended to replace the Monterey Peninsula community’s existing Carmel River and Seaside Groundwater Basin supplies. These supplies have been constrained for decades by legal decisions and habitat concerns, with desalinated seawater. 

The approval of the EIR and EIS are critical to building and operating the MPWSP. The EIR/EIS challenges rejected by the Supreme Court were filed in February 2019 by the City of Marina and the Marina Coast Water District. The environmental reports were prepared by Environmental Science Associates (ESA) under the direction of the California Public Utilities Commission (CPUC) and certified by the CPUC in September 2018.

“The Court’s denial of challenges upholds the EIR/EIS conclusions that the Monterey Peninsula Water Supply Project will have minimal environmental impacts, including on all forms of marine life, and will responsibly resolve the natural resource and community water supply issues,” said Eric Zigas, principal associate and ESA’s Project Manager in a press release.

Faced with regional water restrictions that are among the tightest in the state due to threatened species in the Carmel River and a court-ordered use reduction of the Seaside Groundwater Basin, CalAm urgently needed a reliable, environmentally sound source of water for its Monterey Peninsula customers.

CalAm in 2005 filed its original application with the CPUC to build, own, and operate a desalination plant, pipelines, aquifer storage and recovery, and related facilities. ESA, under contract to the CPUC as the California Environmental Quality Act (CEQA) lead agency, prepared an EIR that allowed the CPUC to approve the Regional Project in 2010.

In 2012, CalAm submitted a revised application with the CPUC. This became the MPWSP, which eventually required ESA to modify and recirculate its Draft EIR as a joint EIR/EIS in coordination with Monterey Bay National Marine Sanctuary (MBNMS). The final EIR/EIS was published in March 2018. It was certified, and the project was approved, by the CPUC in September 2018.

Zigas says it was a long and fascinating challenge to complete the environmental documents.

“The controversial nature surrounding water supply issues in California, and particularly in Monterey, led to a very active stakeholder engagement in the environmental review process, which challenged us to develop a document that advances the scientific assessment of an evolving technology, while meeting diverse expectations,” says Zigas. He says when ESA first began the assignment in 2005, the CPUC granted party status to six organizations. By 2018, there were 26 parties to the CPUC proceeding. “With each issuance of a document by the CPUC, the parties requested greater scientific rigor,” he says.

“We used the EIR/EIS process to partner with other state agencies to understand the project-level implications of interpreting their policy-level guidance, and we used every comment received on the document by any party as a means to develop a more comprehensive and robust document,” says Zigas. “We looked under every rock.”

Poised for final approval, the MPWSP includes subsurface slant wells that would extend offshore into submerged MBNMS lands. Source water would be conveyed inland to a desalination plant, the brine discharged through an existing wastewater outfall, and the desalinated water delivered to Monterey Peninsula customers and/or stored in the Seaside Groundwater Basin. 

Last month CalAm began construction of 5,300 linear-ft of treated water pipeline beneath the pavement within Light fighter Drive and General Jim Moore Boulevard in the City of Seaside in Monterey County. ESA is providing the CPUC and MBNMS with third-party monitoring services to ensure CalAm complies with all mitigation measures identified in the EIR/EIS.

Throughout the remainder of this year and into early 2020, CalAm’s final required permit applications will be considered by the California Coastal Commission, the State Lands Commission, and the Regional Water Quality Control Board. 


Garney Construction of Tracy, CAis installing pipelines, while CDM Constructors will build the desalination plant under a design-build contract. Salt Lake City, Utah-based Boart Longyear will drill the slant wells, Zim Industries will drill the ASR wells, Hal Hays Construction will develop the civil works for the ASR wells, and Mountain Cascade will install the Brine Pipeline.


Monterey Peninsula Engineering will develop the civil works at the slant wells, install the Castroville Return Water Pipeline and the ASR pipelines, and build the Carmel Valley Pump Station.